1. Field of the Invention
The present invention relates to a paper feed mechanism and an image generating apparatus, and more particularly, it relates to a paper feed mechanism and an image generating apparatus each comprising a paper feed cassette and an apparatus body mountable with the paper feed cassette.
2. Description of the Background Art
A paper feed mechanism comprising a paper feed cassette and an apparatus body mountable with the paper feed cassette is known in general, as disclosed in each of Japanese Patent Laying-Open Nos. 8-175696 (1996), 11-29236 (1999), 2001-80763 and 2005-298144 and Japanese Patent No. 3152221, for example.
A paper feeder according to the aforementioned Japanese Patent Laying-Open No. 8-175696 comprises a sheet receiving portion provided parallel to a direction for feeding sheets and a pair of side fences supporting both side surfaces of the sheets. The positions of the pair of side fences can be so controlled that the side fences come into contact with both side surfaces of the sheets. The sheets can be fed to the apparatus body in an unskewed (uninclined) manner by controlling the positions of the pair of side fences so that the side fences come into contact with both side surfaces of the sheets.
The aforementioned Japanese Patent Laying-Open No. 11-29236 discloses a paper feeder (paper feed mechanism) including a pair of tension rollers downwardly pressing transfer papers in paper feeding for inhibiting the transfer papers from movement resulting from paper feeding. The tension rollers downwardly press the transfer papers by the own weights thereof and are provided with high-friction members on portions coming into contact with the transfer papers, thereby applying a load to the transfer papers. Consequently, the load applied to the transfer papers causes back tension when the transfer papers are fed to the apparatus body, thereby correcting skew of the transfer papers.
The aforementioned Japanese Patent Laying-Open No. 2001-80763 discloses an automatic paper feeder (paper feed mechanism) comprising a paper feed roller transporting originals, a paper feed shaft forming the rotating shaft of the paper feed roller and two swing shutters including torque limiters limitedly transmitting the torque of the paper feed shaft. In this automatic paper feeder according to Japanese Patent Laying-Open No. 2001-80763, the two swing shutters push back standby originals until the uppermost original is completely transported, thereby suppressing the standby originals.
In a paper feed mechanism of a liquid injector according to the aforementioned Japanese Patent Laying-Open No. 2005-298144, a receiving portion receiving printed objects includes a paper feed tray lifted up when feeding the printed objects, a reference guide formed parallel to the direction for transporting the printed objects for supporting first side surfaces of the printed objects and an edge guide formed parallel to the reference guide for supporting second side surfaces of the printed objects while remaining unmoved also when feeding the printed objects, and the edge guide is provided with an urging portion having a spring on the base thereof for coming into contact with the second side surfaces of the printed objects on an end closer to the liquid injector. When the printed objects are transported, the paper feed tray is so lifted up that the urging portion presses the printed objects toward the reference guide, whereby the printed objects are transported parallelly to the reference guide. Thus, the printed objects are fed in an unskewed manner.
An automatic paper feeder (paper feed mechanism) according to the aforementioned Japanese Patent No. 3152221 comprises an original set table, a main roller transporting the uppermost original placed on the original set table, a return roller rotating oppositely to the main roller for preventing the main roller from convoluting originals subsequent to the uppermost original and a correction roller coaxial with the return roller for rotating in the same direction as the main roller at a higher transport speed than the main roller. The original set table includes an original butt surface parallel to the direction for transporting the originals on a first side surface thereof, while the main roller, the return roller and the correction roller are arranged closer to the original butt surface than the center of the original set table. While the originals subsequent to the uppermost original are gripped by the return roller, transported oppositely to the direction for transporting the originals and supplied with torque by the return roller to separate from the original butt surface in feeding, the correction roller rotating at the higher speed than the return roller urges the originals toward the original butt surface, thereby aligning the originals parallelly to the original butt surface. Thus, the originals are fed in an unskewed (uninclined) manner.
In the paper feeder described in the aforementioned Japanese Patent Laying-Open No. 8-175696, however, the sheet receiving portion must be separately provided with the pair of side fences movable perpendicularly to the direction for transporting the sheets in order to prevent skew (inclination) of the sheets, and hence the number of components is disadvantageously increased.
In the paper feeder described in the aforementioned Japanese Patent Laying-Open No. 11-29236, the pair of tension rollers including the high-friction members on the portions coming into contact with the transfer papers must be separately provided in order to suppress skew (inclination) of the transfer papers, and hence the number of components is disadvantageously increased.
In the automatic paper feeder described in the aforementioned Japanese Patent Laying-Open No. 2001-80763, the two swing shutters including the torque limiters in shaft holes must be separately provided in order to suppress skew (inclination) of the originals, and hence the number of components is disadvantageously increased.
In the liquid injector described in the aforementioned Japanese Patent Laying-Open No. 2005-298144, the urging portion having the spring on the base thereof must be separately provided in order to suppress skew (inclination) of the printed objects, and hence the number of components is disadvantageously increased.
In the automatic paper feeder described in the aforementioned Japanese Patent No. 3152221, the return roller rotating oppositely to the main roller and the correction roller rotating in the same direction as the main roller must be separately provided in order to suppress skew (inclination) of the originals, and hence the number of components is disadvantageously increased.